Drive finger for vibrating motor



Aug 7, 1962 J. F. WAHL 3,047,948

*1" DRIVE FINGER FOR VIBRATING MOTOR Filed April 8, 1959 INV EN TOR.

JbhlzF Wahl BY Wm W6 United States Patent 3,047,948 DRIVE FINGER FORVIBRATING MOTOR John F. Wahl, Sterling, Ill., assignor to Wahl ClipperCorporation, Sterling, III., a corporation of Illinois Filed Apr. 8,1959, Ser. No. 804,940 3 Claims. (Cl. 30-210) This invention relates toa vibrating motor and more particularly to a drive finger for avibrating motor used in electric hair cutters.

The present subject matter is disclosed but not claimed in my priorco-pending application for Electromagnetic Vibratory Unit, Serial No.734,605, filed May 12, 1958, which issued as Patent No. 2,967,253 onJanuary 3, 1961.

Electric hair cutting instruments, such as hair clippers, which arepowered by electromagnetic vibrating motors have drive elements orfingers which are connected between the free end of the motor armatureand the movable cutting blade to transmit the vibrational movement ofthe armature to the movable cutting blade and cause it to oscillate.

In many instruments of this kind, the drive fingers have other functionsbesides that of simply transmitting motion. For example, they are oftenmade resilient in a direction perpendicular to the plane of vibration ofthe movable cutting blade so that the movable cutting blade may bebiased into the required bearing contact with the fixed cutting blade toestablish a desired cutting relationship between the blades. "Inaddition, the drive fingers may be made resilient in the direction ofthe vibrational motion of the movable cutting blade to permit relativemovement in that direction in order to influence the behavior of thearmature assembly under load and no-load conditions, and particularly toprevent stalling of the armature under severe cutting loads.

Although resilience in the above described direction of vibration isoften desirable, it must be accomplished without appreciably affectingthe path of the movable cutting blade which must oscillate along asubstantially straight line to maintain proper relationship between theblades. If this is not done, the ends of the movable blade tend to whipand extend beyond the margins of the fixed blade. This is likely toinjure the skin of the user.

The desired resilience along only a straight line parallel to the pathof the vibrating movable blade is not easy to achieve in the drivefinger since the free end of the armature assembly vibrates rapidly, andgeneral resilience in the drive finger could cause the above describedwhipping action.

What is needed therefore and comprises the principal object of thisinvention is a drive finger which is resilient in a plane perpendicularto the plane of movement of the movable cutting blade and which permitsresilient relative movement between the armature and the movable cuttingblade only along a substantially straight line which is parallel to thepath followed by the movable cutting blade.

These and other objects of this invention will become more apparent whenread in the light of the accompanying drawings and specificationwherein:

FIG. 1 is a perspective view showing the end of an armature with thedrive finger attached and with arrows indicating its resilience in aplane parallel to the plane of vibrational movement of the armature.

FIG. 2 is an end elevational view, partly in section, of a portion ofthe armature and drive finger with a movable cutting blade attached,showing by means of arrows the resilience of the drive finger in a planeperpendicular to the vibrational plane of the movable cutting blade.

FIG. 3 is a sectional view on line 33 of FIG. 2.

FIG. 4 is a sectional view of a modified drive finger embodying thefeatures of this invention.

3,047,948 Patented Aug. 7, 1962 Referring now to FIGS. 1, 2 and 3 of thedrawings, one embodiment of a drive finger constructed according to theprinciples of this invention is indicated generally by the referencenumeral 10. This drive finger may be formed from unitary, fiat, thin,resilient, sheet material, usually metal, and before forming may besubstantially T-shaped, although that shape is not critical, and othersare contemplated. For example, an initial rectangular shape properlyslotted would be quite practical. As understood in the art, finger 10 ismounted to transmit vibratory motion in the directions indicated by thearrows A in FIG. 1 from a vibratory armature 20 to a movable blade 32(FIG. 2) of an electric hair cutter.

Drive finger 10, in this particular embodiment, includes an elongatedstem or arm portion 12, a base portion 16 and oppositely projecting armportions 1414. As shown by its shape, the cross sections of the stem orarm portion 12 transverse to its direction of elongation are straightand parallel to each other so that the drive finger is resilient toforces applied to it which are perpendicular to its surface and rigid toforces applied to it which are parallel to its surface.

In vibratory motors used in hair cutting instruments, the armaturevibrates, and since its thickness is not significant, the armature maybe described as vibrating in a plane. Base portion 16 of stem or armportion 12 of drive finger 10 is connected to vibrating armature 20 insuch a way that stem portion 12 is resilient to forces applied to itwhich are perpendicular to the vibrating plane of armature 20.Consequently stem portion 12 of drive finger 10 is rigid to forcesapplied to it in directions Parallel to the vibrating plane of thearmature and perpendicular to the direction of elongation of the stem orarm portion. The above described resilience may be used to provide therequired cutting bias or tension between the fixed and movable cuttingblades described below.

In addition, the rigidity of drive finger 10 in the direction describedabove permits stem or arm portion 12 to withstand the large inertialforces produced by the rapid vibratory motion of the armature andmovable blade without bending or whipping, in a plane parallel to thevibratory plane of the armature, around its connection with thearmature. The direction of these inertial forces applied to drive finger10 is indicated by arrows C in FIG. 1.

Stem portion 12 may be bent at 13 to control the magnitude and directionof the bias between the fixed and movable blades, and this direction isindicated by arrows B in FIG. 2.

As seen, base 16 may be enlarged and provided with openings 18, so thatdrive finger 10 may be secured firmly to the free end of armature 20 byany conventional means such as screws or rivets 17, see FIG. 2.

The oppositely extending arm portions 1414 disposed on the free end ofstem portion 12 opposite to the base portion 16 project from a commoncentral section 22. Arm portions 1414 are bent substantiallyperpendicular to central section 22 to form a pair of spaced parallelflanges 24 which extend in a direction parallel to the direction ofelongation of the central section 22. Since these flanges are alsoformed from the same resilient sheet material, they will be resilientmainly to forces applied to it which are perpendicular to their surface.

As seen in FIG. 1, this means they will be resilient to forces parallelto the vibrating plane of armature 20, see the arrows D in FIG. 3. Thefree ends 26 of flanges 24 in this particular embodiment are bent towardeach other in a plane parallel to the plane of the common centralsection 22. These free ends are adapted to be secured in suitablemanner, as by molding, to plastic member 30 which engages movablecutting blade 32 of the hair cutting instrument. As seen, movable blade32 vibrates along a line or path parallel to the cutting portion offixed blade 33.

This arrangement introduces a resilient between armature 20 and movablecutting blade 32 in the vibratory plane of the armature so that theoperation of the vibrating motor under load and no-load conditions maybe optimized and armature stall under severe loads may be eliminated. Atthe same time, since the length of the flanges 24 is small in comparisonto the length of stem portion 12, any pivoting movement of these flangesaround an axis defined by their edge connection to central section 22will produce only insignificant deviations from the straight line motionof the movable cutting blade.

A modified drive finger 40 is shown in FIG. 4. This drive finger mayinitially be T-shaped, but in this construction downwardly facingU-shaped flanges 42 including upwardly bent arms 1414' are formed on theends of common central section 44. The extreme ends 46 of flanges 42 arebent toward each other in a plane par allel and closely adjacent to theplane of the common central section 44. Ends 46 are adapted to beconnected to a plastic member (not shown) like that described inconnection with the form shown in FIGS. 1-3.

This modification in which central section 44 is closely adjacent toends 46 of flanges 42 is useful when space limitations in a particularcutter forbid the employment of the drive finger shown in FIG. 1 withthe comparatively large separation between common central section 22 ofthe arms 14-44 and ends 26 of flanges 24. Furthermore, despite any spacelimitations which may be encountered, the overall length of flanges 42may be made equal to or greater than the length of flanges 24 in drivefinger so the modified drive finger may be used to provide any desiredresilience between armature and movable cutting blade 32 in planesparallel to the vibrating plane of the armature.

The invention may be embodied in other forms without departing from thespirit or essential characteristics thereof as set forth in the claims,and the present embodiment is therefore to be considered as illustrativeand not restrictive, and it is intended to include all changes whichcome within the scope and range of the claims.

I claim:

1. In a hair cutting instrument having a fixed blade, a cooperatingmovable blade and a motor including a vibratory armature having a freeend spaced from said movable blade; a drive finger of resilient sheetmaterial extending between said armature free end and said movable bladeand connected rigidly to said free end and to means rigidly engagingsaid movable blade, the portion of said drive finger adjacent saidarmature free end having its width dimension parallel to the plane ofarmature vibration whereby said portion is rigid to forces parallel tosaid plane and resilient to forces normal to said plane, said formercharacteristic effective to prevent blade whipping and said lattercharacteristic effective to provide cutting bias between said blades,the portion of said drive finger adjacent said movable blade extendingfrom said first portion and having a width dimension lying in a planegenerally perpendicular to said first portion and to the path of saidmovable blade whereby said last portion is rigid to forces tending totwist same and resilient to forces parallel to said path, said formercharacteristic further effective to prevent blade whipping and saidlatter characteristic eifective to prevent motor stall when theinstrument is subjected to heavy mechanical load.

2. The combination of claim 1 wherein said last portion comprises a pairof spaced flanges having width dimensions normal to forces parallel tothe path of said movable blade, the free ends of said flanges rigidlysecured to plastic means adapted to seat rigidly within a recess in saidblade.

3. The apparatus set forth in claim 2 wherein said flanges are U-shapedto increase the length thereof without causing a corresponding increasein a dimension of the drive finger.

References Cited in the file of this patent UNITED STATES PATENTS1,596,294 N'orstrom Aug. 17, 1926 2,082,402 Kusnarowis June 1, 19372,265,932 Wahl Dec. 9, 1941 2,304,525 Andis Dec. 8, 1942 2,668,351 Andiset al. Feb. 9, 1954 2,876,538 Wahl et al. Mar. 10, 1959

